Various methods have been proposed so that injected fluids can be diverted to uncontacted zones of a reservoir. One such method is disclosed in U.S. Pat. No. 2,402,588 issued to Andresen. This patent discloses a method of sealing a more permeable area of the reservoir by injecting into a reservoir a dilute alkaline solution of sodium silicate under low pressure. An acid gas such as carbon dioxide is then injected to reduce the alkalinity of the solution, resulting in gelling.
Another method is disclosed in U.S. Pat. No. 3,645,336 issued to Young et al. This patent teaches the plugging of a zone of a reservoir by injecting a mixture of steam and sodium silicate into the permeable zone. A second mixture containing steam and a gelling agent such as carbon dioxide is injected into the permeable zone, and the two mixtures are allowed to react. A hard silica gel plug is formed.
Yet another method is disclosed in U.S. Pat. No. 3,805,893 which issued to Sarem. Sarem discloses the formation of a gelatinous precipitate by injection of small slugs of dilute aqueous alkaline metal silicate solution, followed by water and then a dilute aqueous solution of a water soluble material which reacts with the alkali metal silicate to form a precipitate. The precipitate hardens to form a substantially impermeable substance.
U.S. Pat. No. 3,965,986 issued to Christopher discloses still another method. Here, a slug of fumed colloidal silica and water is injected into a reservoir. This slug has a relatively low viscosity. A surfactant is then injected which forms a gel on contact with the silica slug.
Meyers et al. disclosed a method for reducing the permeability of a subterranean formation in U.S. Pat. No. 4,676,318. Here, an alkali metal silicate was produced by injecting into the formation a solution of alkali metal silicate and a chemical surfactant, along with a non-condensible gas. The foam hardens into a substantially impermeable solid. The foam may be used to reduce permeability in areas of the formation which have been steam swept during steam stimulation cycles. Thus, subsequent steam stimulation cycles were directed to uncontacted areas of the formation.
Many of the materials proposed for profile control of injected or produced fluids have been polymer hydrogels. These gels are formed either in-situ or ex-situ by blending 100 to 10,000 ppm of a water soluble polymer with an appropriate cross-linker. These types of gels are advantageous in many situations because their dilute polymer concentration makes them relatively inexpensive. However, their water soluble nature and relatively low elastic limits may render them inappropriate for profile control in extremely high flow rate or high pressure applications such as a plugging of a hydraulically-induced fracture.
Therefore, what is needed is a water-external component system which will have a very high elastic limit or compressive strength so as to be able to resist high pressure and high fluid flow within a formation.